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"Saying with pride that the missile's rate of hits is very accurate and Pukguksong-2 is a successful strategic weapon, he approved the deployment of this weapon system for action," KCNA said, quoting leader Kim Jong Un.

The launch verified the reliability and accuracy of the solid-fuel engine's operation and stage separation and the late-stage guidance of the nuclear warhead which was recorded by a device mounted on the warhead, KCNA said.

"Viewing the images of the Earth being sent real-time from the camera mounted on the ballistic missile, Supreme leader Kim Jong Un said it feels grand to look at the Earth from the rocket we launched and the entire world looks so beautiful," KCNA said.

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The missile test was broadcast around the country (Image: AFP/Getty Images)

The use of solid fuel presents great advantages for weapons because the fuel is more stable and can be transported easily in the missile's tank allowing for a launch on very short notice.

The Pukguksong-2 missile flew about 500 km (310 miles), reaching an altitude of 560 km, and landed in waters off the North Korea's east coast, South Korea's military said on Sunday.

On Monday, the South's military said the test provided more "meaningful data" for the North's missile programme but whether the North mastered the re-entry technology for the warhead needs additional analysis to verify the North's claims of advances.

North Korea boasts that it is ready for nuclear war (Image: AFP)

The reclusive state has been working to develop a nuclear-tipped missile capable of striking the US mainland.

On Saturday, it said it had developed the capability to strike the US mainland, although Western missile experts say the claim is exaggerated.

The North has yet to demonstrate it has successfully miniaturised a nuclear warhead to mount on a ballistic missile despite claims to having mastered the technology.

On Monday, KCNA said the latest test follows the successful test last week of another missile that has put Hawaii and Alaska within range.

The missiles are believed to be capable of hitting US targets (Image: AFP/Getty Images)

Experts say solid fuel engines and mobile launchers make it more difficult to detect signs of launch preparations.

"For military purposes, solid-fueled missiles have the advantage that they have the fuel loaded in them and can be launched quickly after they are moved to a launch site," David Wright, co-director of the Global Security Program at the U.S.-based Union of Concerned Scientists, said in a blog post.

"Building large solid missiles is difficult," he said, adding it took decades for major superpowers such as France and China to go from a medium-range missile to an intercontinental ballistic missile.

"So this is not something that will happen soon, but with time North Korea will be able to do it," Wright said.

An official travelling with President Donald Trump in Saudi Arabia said the White House was aware of the latest launch and noted that the missile had a shorter range than the three previous missiles that North Korea had tested.

Donald Trump was made aware of the latest missile launch (Image: AFP)

US Secretary of State Rex Tillerson said economic and diplomatic pressure would continue to be applied to North Korea.

"We can not absolutely tolerate the missile launch on May 21 and repeated provocative remarks and actions by North Korea," Japan's Chief Cabinet Secretary Yoshihide Suga said on Monday.

"It is important to lower North Korea’s foreign currency earnings and prevent nuclear missile related shipment and technological transfer in order to prevent North Korea’s nuclear missile development. We will fully implement our own sanctions against North Korea."

The two missile tests in a week complicate plans by South Korea's new President Moon Jae-in to seek ways to reduce tension on the peninsula.

Moon took office on May 10 after winning an election on a platform of a more moderate approach to the North, with which the South is still technically at war since no peace treaty was signed at the end of their 1950-1953 conflict.

On Monday, the South's Unification Ministry spokesman Lee Duk-haeng said while Seoul will respond firmly to any provocations by the North, "it would not be desirable to have ties between the South and the North severed."

Requests by South Koreans to resume exchange with the North will be considered "flexibly" within the range such interaction will not violate any existing sanctions, Lee added.

All civilian exchange across the border has been suspended following toughed bilateral sanctions imposed by Seoul last year.

The South halted a decade of improving ties in 2010 after the sinking of a South Korean navy ship, which Seoul has blamed on the North. Pyongyang denies any involvement.